Dr Böhm – Digital Drums dual restoration

It does not happen very often for two rare vintage drum machines to turn up at the same time and both suffered exactly the same fate. Internal NiCd backup battery cell leaked out its potassium hydroxide contents and eaten away several of the traces.

One case was rather mild and only suffered localized corrosion. I had to replace about 5 smaller IC sockets, thoroughly clean it, neutralize with Vinegar and the only reconstruct few traces and mainly the vias connecting top and bottom side of the PCB. The other instrument was in much worse situation, it was repaired at some point in time but because the leak wasn’t neutralized but probably just wiped away it spread the corrosion across entire length of the PCB. I was quite desperate because this would require massive surgery, I would have to re route dozens of tracks and i was worried even that wouldn’t last for long given how severe the corrosion was.

Lucky enough my friend Miro Ruml offered he would clone the circuit board, not the task for the faint hearted but to quote his words “I prefer it to crosswords or Sudoku! “

The first prototype.

After some 50 hours of design and fault finding tedious work the unit sprung to life. There were only 8 routing errors made but I had the new version 2 of the PCB made. (if you’d like to buy one, please contact me, price is 70EUR per piece, still beats the time one would spend reconstructing heavily corroded PCB).

Its quite rare to see the version with accompaniment fitted and in this case both of the units had it. It is a whole separate CPU with its own ROM and RAMS, in a fact the accompaniment is much more complex circuitry then the drum machine itself. Those two computers are linked via serial interface and allow for quite interesting features.